Some internal combustion engines utilize a compression device such as a turbocharger to increase engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side of an engine and the compressor is coupled to an intake manifold side of the engine. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure (e.g. boost, or boost pressure) in the intake manifold and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. An actuator may be operatively coupled via a linkage to a wastegate valve and driven to position the wastegate valve anywhere between a fully open position and a fully closed position (e.g., at a valve seat) to achieve the desired boost based on operating conditions. The actuator may be an electric actuator such as a motor, for example. A position sensor may provide feedback indicating the location of the actuator relative to a reference point. Depending on surrounding conditions, the linkage may be subjected to significantly large forces, vibration, and temperatures.
In some approaches, a wastegate valve is coupled to a wastegate actuator via a four-bar linkage, separating the actuator from the valve by a distance in order to protect the actuator from high temperatures proximate the valve. In this manner, actuator degradation that otherwise might result from such high temperatures may be prevented. Further, lash in the gears and/or linkage can create measurement errors due to the separation of the measurement from the valve itself. Other types of linkages may couple a wastegate valve to an associated actuator, however, such as a linear rod.
The inventors herein have recognized a problem with such approaches. Thermal deformation including expansion and contraction may take place in the turbocharger and linkage as component temperature vary and particularly increase. Further, thermally-induced movement of the valve seat may occur, thereby moving the seat relative to the actuator, linkage, and measurement of the wastegate valve. Thus, in some scenarios, thermal and mechanical deformation may occur in a wastegate assembly at regions other than the linkage itself, which may alter the position of a valve seat against which a wastegate valve is abutted at its fully closed position when the supply of boost is not desired. Such variation in the geometric properties of linkages and valve seats reduce the accuracy with which a wastegate valve may be positioned, in turn reducing the accuracy of boost supply. Further, a linkage may deflect (e.g., bend) when subject to relatively high forces including those applied to the linkage by an actuator and/or exhaust forces due to the surrounding environment.
Methods for compensating variation in the geometry and position of linkages and valve seats in wastegate assemblies are thus provided.
In one example, a method of operating a wastegate in an internal combustion engine comprises, at engine startup, placing a wastegate valve at a seat, recording a position of the seat and associating the seat position with one or more operating parameters, and modifying a position of a wastegate actuator based on the seat position throughout engine operation.
In a more specific example, the method further comprises recording a plurality of seat positions and associating each of the plurality of seat positions with the one or more operating parameters as the wastegate valve is placed at the seat throughout engine operation.
In another aspect of the example, the method further comprises as the wastegate valve is placed at the seat throughout engine operation, incrementing the position of the wastegate actuator by adding a current margin to a current presently supplied to the wastegate actuator, and estimating deflection in a linkage coupling the wastegate valve to the wastegate actuator based on change in output from a wastegate actuator position sensor, the change in output resulting from incrementing the position of the wastegate actuator.
In still another aspect of the example, placing the wastegate valve at the seat includes retrieving a previously-recorded seat position from the data structure, placing the wastegate valve at the previously-recorded seat position, incrementing the position of the wastegate actuator by adding a current margin to a current presently supplied to the wastegate actuator, and recording a current seat position once output from a wastegate actuator position sensor falls below a threshold.
In the examples described above, variation in wastegate valve seat position, linkage geometry (e.g., deflection, thermal expansion/contraction), and overall wastegate assembly geometry which would otherwise result in inaccurate wastegate valve positioning is compensated. Positions of the wastegate actuator may be modified based on determined valve seat positions. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.